When centrifugation processing is performed on a blood collection tube containing a blood specimen and a separating agent, the blood specimen becomes separated inside the blood collection tube into blood serum and blood clotting factor located on respective sides of the separating agent. For example, centrifugal force is applied in the direction toward the bottom of the blood collection tube, which results in the blood clotting factor, separating agent, and serum being separated from each other inside the blood collection tube and present in that order from the bottom. Subsequently, from inside the blood collection tube after being subjected to centrifugation, the serum is removed using a dispensing device or the like, and testing and analysis are performed on the serum remaining inside the blood collection tube and the serum removed from the blood collection tube.
For the testing and analysis of the serum remaining inside the blood collection tube, the serum must remain in a quantity required for the testing and analysis. However, although the quantity of serum removed from the blood collection tube can be relatively easily determined based on the suction volume of the dispensing device or the like, determining the remaining quantity of serum inside the blood collection tube is not easy.
For example, Patent Document 1 discloses a technique for detecting the separation position of the serum separated inside a test tube. If the serum separation position can be detected, the quantity of serum can be calculated based on the serum separation position, data on the shape of the test tube, and the like, for example. However, detection of the separation position is not easy and requires a complex detection device and the like.
Meanwhile, a hematocrit value, which indicates a ratio of volume occupied by blood cells in blood, is known as a medical numerical value. Patent Document 2 discloses a technique of using the hematocrit value to estimate the interface position (separation position) in a separated blood specimen.